Johan Santana, rocked by the Yankees last year in one of the worst starts in his career, will be out for a little revenge when he takes the mound in Sunday night’s series finale. Photo: JASON SZENES/ NY POST

It could be an opportunity or a burden, but you can excuse beaten-down Mets fans if they see it as the latter.

With the start of interleague play tonight comes the start of six matchups between the Mets and Yankees. Unfortunately for the Mets, they are the only National League team that has to play the Yankees six times every year. And the Yankees just happen to be the best team in baseball over the past 13 seasons.

Bobby Valentine managed the Mets in the first six Subway Series and embraces the event, but admits it is a bit unfair for his former team.

“The only bad thing about it is the Mets always have to play against the Yankees,” said Valentine, now an analyst on ESPN’s “Baseball Tonight.”

“Sometimes one game does mean a difference moving on to the postseason or not. The teams the Mets are competing against don’t necessarily have to play the Yankees every year.”

Nevertheless, Valentine said it will provide a chance for the Mets to jumpstart their 2010 season. The Mets were in first at the start of May, but now find themselves in last place in the NL East and fresh off a visit from COO Jeff Wilpon, which most saw as a warning to manager Jerry Manuel that he better turn things around and quickly.

“That little extra impetus whether it’s artificial or real makes a difference,” said Valentine, who was the manager when the Mets lost to the Yankees in the 2000 World Series.

“Everyone knows it’s only another series, three games in the standings, but when you are trying to accomplish an identity level and all identity deals with respect, it can only help when you do well against the world champion Yankees.”

They didn’t last year. In a season filled with tough-to-swallow losses, the ultimate one came in the Subway Series opener when Luis Castillo dropped an Alex Rodriguez pop up with two outs in the ninth, allowing the tying and winning runs to score. Two days later, the Yankees battered Mets ace Johan Santana, who will start this Sunday in a matchup against CC Sabathia, in a 15-0 rout. When the series shifted to Citi Field, the Mets were swept and scored three runs in the three games and dropped their overall Subway Series record to 30-42.

Valentine had his own Subway Series nightmare. In 1999, general manager Steve Phillips fired three of Valentine’s coaches after the Mets lost the first two games against the Yankees that brought their losing streak to eight games.

“Our team was 27-20 and that was as good as any team in the league,” Valentine said. “We had an eight-day run where nothing was going right. The balls weren’t falling and the other team’s were.”

Manuel has been facing similar pressure as this weekend’s series with the Yankees approaches.

“Our team went to one under .500 at 27-28 and a reporter asked me what we would do the next 55 games and I said 40-15,” Valentine said. “Al Leiter pitched a great game against the Yankees and away we went on a 40-15 run. Maybe Jerry should try making the same prediction.”